(1) Field of the Invention
The present invention relates to a steering apparatus for a front wheel drive tractor, and more particularly to a steering apparatus including a transmission structure between a front axle and a front wheel hub shaft.
(2) Description of the Prior Art
A known front wheel drive tractor comprises front wheels disposed at opposite ends of a front axle case and steerable about kingpins through transmission cases. Each of the transmission cases is disposed inside a rim of the front wheel, and contains a transmission operatively connecting the front axle to the front wheel.
Front wheels of an ordinary passenger car have a camber angle of about 2.degree. to prevent shimmy during a high speed run. The front wheels of the known tractor noted above also have a camber angle of about 2.degree. although the tractor does not run at high speed unlike a passenger car.
Soft tyres are used on wheels of the ordinary passenger car. Therefore, the inclination of the front wheels with upper portions thereof disposed laterally outwardly as noted above does not result in partial wear of front wheel tyres, i.e. wear that is more conspicuous in laterally outward portions than in other portions of the tyres. However, the tractor uses hard tyres, and the front wheel inclination noted above presents the problem of conspicuous partial wear occurring to laterally outward portions of the front wheel tyres.
In order to prevent the partial wear of the front wheel tyres of the tractor, it is conceivable to eliminate the camber angle of the front wheels since the tractor does not run at high speed as does the ordinary passenger vehicle. However, such a modification alone would result in the lower portions of the right and left transmission cases greatly projecting from inside the front wheels, and in a corresponding reduction of spaces below the transmission cases. This would give rise to the problem that the tractor is not fit for an agricultural operation to be carried out while straddling a large ridge.